Description
In the context of 3GPP standards, a Geostationary Earth Orbit (GEO) refers to a specific orbital path used by satellites that are integrated as access nodes within a 3GPP-defined Non-Terrestrial Network (NTN). A GEO satellite is positioned at an altitude of roughly 35,786 kilometers directly above the Earth's equator, moving in the same direction as the planet's rotation. This synchronization results in an orbital period of exactly 24 hours, causing the satellite to remain fixed in the sky relative to an observer on the ground. This stationary characteristic is its defining operational feature.
From a network architecture perspective, a GEO satellite in a 3GPP NTN acts as a radio base station, often referred to as a gNB in 5G terminology, or as a transparent payload that relays signals. It connects User Equipment (UE) on the ground to a ground-based gateway station, which is then connected to the 5G core network. The communication link involves a Service Link (between the UE and satellite) and a Feeder Link (between the satellite and the gateway). Due to the immense distance, GEO links introduce a very high propagation delay of approximately 250 milliseconds for a round trip, which is a critical design constraint impacting protocols and services. The large coverage footprint of a single GEO satellite (covering up to a third of the Earth's surface) is a major advantage for providing ubiquitous coverage over oceans, deserts, and other unserved areas.
3GPP specifications have been adapted to support GEO-based NTN. This involves enhancements to cope with the long delay and high Doppler shift (which is relatively low for GEO but still present), timing advance procedures, mobility management (as handovers are less frequent due to the wide beam), and specific radio resource management techniques. The physical layer specifications (e.g., in 38.101, 38.108) define supported frequency bands and requirements for GEO operation. The system must handle the challenge of link budget due to the long distance, requiring UEs with enhanced capabilities or specialized terminals for reliable connectivity.
Purpose & Motivation
The standardization of GEO satellite operation within 3GPP, starting in Release 12 and significantly expanded for 5G NTN, is driven by the goal of providing seamless, global wireless coverage. Traditional terrestrial networks (cells on towers) are economically and physically impractical for covering vast rural, maritime, and aerial regions. GEO satellites solve this problem by offering a single platform that can provide continuous coverage to an entire continent or ocean basin, filling critical coverage gaps and enabling true ubiquitous connectivity for 5G.
Historically, satellite communication existed as a separate, non-integrated system. The motivation for integrating GEO (and other orbits like LEO and MEO) into 3GPP standards is to unify terrestrial and non-terrestrial networks under a common framework. This allows mobile devices to potentially connect directly to satellites using modified 3GPP protocols, enabling services like emergency communications, IoT asset tracking in remote areas, and backhaul for rural base stations. It addresses the limitations of purely terrestrial networks by ensuring service continuity everywhere, which is essential for mission-critical communications, disaster recovery, and connecting the unconnected, thereby supporting the United Nations' sustainable development goals for universal internet access.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (177 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-12, normative work from Rel-15.
In Release 15, the GEO function was introduced as part of the broader satellite access framework, specifically enabling a 5G satellite access network using geostationary orbits. This included defining the serving satellite concept for static orbital scenarios and supporting service continuity for UEs within its coverage. The release also established requirements for NG-RAN sharing and multicast/broadcast services specifically over this satellite access network.
In Release 16, the GEO function introduced support for national or regional regulatory requirements specifically for satellite access. This was complemented by new technical capabilities enabling a satellite NG-RAN to support RAN sharing between satellite and terrestrial network operators. Furthermore, the release formalized the "Store and Forward" (S&F) satellite operation, allowing the 5G system to provide service by storing and forwarding data when a satellite feeder link is temporarily unavailable.
- National or regional regulatory requirements for satellite access TS 22.261CR0363
In Release 17, 3GPP introduced specific support for GEO satellite operations by defining new 5GMM procedures and extended NAS timers to handle the unique latency and coverage characteristics of geostationary satellite access. The release standardized the "Satellite Backhaul Change" as a new policy control event and introduced a dedicated 5QI for satellite access to enable appropriate QoS handling. Furthermore, it added capabilities for network selection and PDU session establishment specifically for NR satellite access, ensuring service continuity and efficient resource usage across these networks.
- Performance requirements for satellite access TS 22.261CR0428
- Network selection for NR satellite access TS 23.501CR0254
- Support of new RATs in 5GS integrating satellite access TS 23.501CR2781
- Indicating a last visited TAI in a Registration for NR Satellite Access TS 23.501CR3379
- Term definitions for satellite access TS 24.301CR3664
- Addition of extended NAS timers via a satellite access TS 24.301CR3687
+ 39 more changes
In Release 18, key enhancements for the GEO function included the support of local switching via a UPF deployed on the satellite for GEO backhaul cases, enabling more efficient UE-to-UE communication directly via the satellite without ground segment traversal. Additionally, the release introduced mechanisms for provisioning satellite coverage availability data to the AMF and UEs to aid in network and mobility management. These updates were complemented by the formal addition of a dedicated GEO satellite identity type for network operations.
- Requirements for satellite backhaul TS 22.261CR0525
- Update to KPIs to 5G system with satellite access for support control and/or video surveillance TS 22.261CR0519
- Support of Satellite Edge Computing via UPF deployed on satellite TS 23.501CR3793
- Support of local switch via UPF deployed on satellite for GEO backhaul case TS 23.501CR3794
- QoS Monitoring for Dynamic Satellite Backhaul TS 23.501CR3803
- Transfer of Satellite Coverage Data to a UE and AMF TS 23.501CR3956
+ 49 more changes
In Release 19, key GEO satellite enhancements included the formalization of Store and Forward (S&F) satellite operation, defining procedures for attach, tracking area update, and detach specific to this intermittent connectivity mode. The release also introduced support for UE-Satellite-UE communication, enabling direct data relay between UEs via the satellite without ground segment traversal, including mechanisms for serving satellite identification during these connections. Furthermore, it added satellite NG-RAN and satellite E-UTRAN into the RAT utilization control framework and specified procedures for a regenerative payload with an NG-RAN node onboard the satellite.
- Add Security and Charging aspects for Satellite in TS 22.261 TS 22.261CR0700
- New section for Satellite access in 22261 TS 22.261CR0697
- Add remaining consolidated requirements of Satellite Access TS 22.261CR0747
- Support of Regenerative Payload with NG-RAN Node Onboard Satellite TS 23.501CR5622
- Support of UE-Satellite-UE communication TS 23.501CR5583
- Support of UE-satellite-UE communications when serving satellite changes TS 23.501CR5518
+ 59 more changes
In Release 20, key enhancements for the GEO function included new requirements for satellite access network sharing via Indirect Network Sharing and the introduction of a Resilient Notification Service to inform users of missed services when unreachable via satellite. The release also brought specific clarifications and performance corrections for IMS-based GEO Global Call Services, including IMS Voice over GEO and Voice over GEO Call Setup Time, alongside technical corrections for propagation and end-to-end latency via satellite.
- New requirements for satellite access network sharing via Indirect Network Sharing TS 22.261CR0795
- Resilient Notification Service for 5G Satellite access. TS 22.261CR0825
- Broadcast Service with satellite access for unregistered UEs TS 22.261CR0835
- Enhancements for IMS-based GEO Global Call Services TS 22.261CR0817
- Requirements for enhanced positioning using satellite access TS 22.261CR0830
- CR on IMS Voice over GEO clarifications TS 22.261CR0852
+ 3 more changes
Explore further
Broader topics and technologies where GEO plays a role.
Defining Specifications
3GPP specifications that define or reference GEO, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 22.261 vk30 | 5G System Service Requirements | Rel-20 |
| TS 22.822 vg00 | Satellite Access in 5G Study | Rel-16 |
| TS 22.887 vk00 | Study on satellite access - Phase 4 | Rel-20 |
| TS 23.008 vj00 | Organization of Subscriber Data | Rel-19 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TR 23.737 vh20 | Satellite Access in 5G Architecture Study | Rel-17 |
| TR 23.799 ve00 | Study on Next Generation System Architecture | Rel-14 |
| TS 24.301 vj60 | NAS protocol for Evolved Packet System | Rel-19 |
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 25.172 vj00 | A-GANSS UE Minimum Performance Requirements (FDD) | Rel-19 |
| TS 25.173 vj00 | A-GANSS Performance Requirements (TDD) | Rel-19 |
| TR 28.808 vh00 | 5G satellite integration management study | Rel-17 |
| TR 28.841 vi01 | Technical Report on IoT NTN Enhancements | Rel-18 |
| TS 28.874 vj10 | Study on Management Aspects of NTN Phase 2 | Rel-19 |
| TS 29.212 vj00 | Gx/Gxx/Sd/St Diameter Protocol | Rel-19 |
| TS 29.512 vj40 | 5G Session Management Policy Control Service | Rel-19 |
| TS 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | Rel-19 |
| TS 29.523 vj20 | 5G Policy Control Event Exposure Service | Rel-19 |
| TS 29.571 vj50 | Common Data Types for 5G Service Based Interfaces | Rel-19 |
| TS 36.102 vj10 | E-UTRA UE Satellite Access RF Requirements | Rel-19 |
| TS 36.108 vj10 | Satellite Access Node RF Requirements | Rel-19 |
| TS 36.171 vj10 | A-GNSS Minimum Performance Requirements for UE | Rel-19 |
| TS 36.181 vj30 | E-UTRA RF Test Methods for Satellite Access Node | Rel-19 |
| TS 36.521 vj00 | E-UTRA UE Conformance ICS Proforma | Rel-19 |
| TR 36.763 vh00 | NB-IoT/eMTC Support for Non-Terrestrial Networks | Rel-17 |
| TS 37.571 vj00 | UE Conformance for Positioning | Rel-19 |
| TS 38.101 vj31 | NR User Equipment Radio Transmissions | Rel-19 |
| TS 38.108 vj20 | NTN NR Satellite Access Node RF Requirements | Rel-19 |
| TS 38.171 vj10 | 5G A-GNSS UE Positioning Requirements | Rel-19 |
| TS 38.181 vj10 | NR Satellite Access Node RF Testing | Rel-19 |
| TS 38.521 vj20 | NR Physical Layer UE Conformance Testing | Rel-19 |
| TS 38.741 vj00 | NTN L-/S-band for NR Technical Specification | Rel-19 |
| TS 38.811 vf40 | Study on NR Support for Non-Terrestrial Networks | Rel-15 |
| TS 38.821 vg20 | NR Support for Non-Terrestrial Networks | Rel-16 |
| TS 38.863 vj10 | NR NTN RF and Co-existence Spec | Rel-19 |
| TR 38.913 vj00 | Next Gen Access Tech Scenarios & Requirements | Rel-19 |